(a) Field of the Invention
This invention relates to optical device modules and particularly relates to optical device modules including an optical device, a flexible substrate connected to the optical device and electronic componentry mounted on the flexible substrate.
(b) Description of the Related Art
In recent years, optical device modules have been developed in which an optical device having a light receiving/emitting function and a drive circuit for the optical device are integrated. Examples of such an optical device module include optical pickups used as for reading DVDs with the optical device and camera modules for mobile phones. There is a demand for these optical device modules to be downsized according to size reduction of built-in components.
More specifically, examples of the above optical device module are solid-state image sensing device modules (image sensing modules) using as an optical device a solid-state image sensing device, such as a charge-coupled image sensing device (CCD), a static induction transistor image sensing device (SIT) or a charge modulation image sensing device (CMD). These solid-state image sensing device modules are often built in compact camera units. These solid-state image sensing device modules are used in a manner incorporated in a hardened tip of an insertion tube inserted in the compact camera unit. Such a compact camera unit is demanded to have a tip shorter and narrower in outer diameter because of use in archeological excavation, for search for narrow spaces in disasters and for internal investigation of artifacts. From this point of view, it is important how a solid-state image sensing device module is downsized. In addition, in order to release compact camera units at low price, it is also an important challenge to improve the assembly efficiency of solid state image sensing device modules and thereby save the production cost.
There is known a solid-state image sensing device module intended to attain size reduction and cost saving, wherein leads on a flexible substrate having an IC and a chip component mounted thereon are bent and connected to bumps on a particular edge of a solid-state image sensing device and the back surface of the IC is adhered to the back surface of the solid-state image sensing device (see, for example, Published Japanese Patent Application No. H11-271646).
FIG. 13 is a conceptual cross-sectional view showing the structure of the known solid-state image sensing device module disclosed in the above document.
As shown in FIG. 13, first, a solid-state image sensing device 102, a semiconductor device (an IC chip) 103, a chip component 104 are mounted on a flexible substrate 101 and the flexible substrate 101 is connected to external signal lines 105. Thereafter, the flexible substrate 101 is bent at right angles at three locations so that the bottom surface of the solid-state image sensing device 102 and the top surface of the IC chip 103 are opposed to each other. Both the surfaces are adhered to each other by an adhesive 122. Then, the side surfaces of the chip component 104 are adhered to opposed parts of the bent substrate 101 by unshown adhesive. In this manner, a solid-state image sensing device module for an electronic endoscope is formed with a compact configuration. The above Published Japanese Patent Application No. H11-271646 describes that since the solid-state image sensing device module is configured by bending the flexible substrate 101 in a rectangular shape and adhering the back surfaces of the IC chip 103 and the solid-state image sensing device 102 to each other, this provides size reduction and cost saving without deteriorating working efficiency.
There is also known another solid-state image sensing device module intended to attain size reduction, wherein a flexible substrate is bent in the shape of a box, electronic components are mounted on the flexible substrate inner surfaces of the box shape and a solid-state image sensing device is connected to terminals on the bottom of the flexible substrate (see, for example, Published Japanese Patent Application No. 2000-210252). The Published Japanese Patent Application No. 2000-210252 describes that since the flexible substrate is bent in the shape of a box all surfaces of which are rectangular and electronic components are mounted on the substrate inner surfaces of the box shape, the image sensing unit can be downsized, thereby narrowing and downsizing the endoscope tip.